Oral morphine remains the drug of choice for most patients with
severe cancer pain, and the sustained-release form (MS-Contin,
Roxanol SR), has certain advantages, Ronald Blum, MD, said at
a conference sponsored by Cancer Care, Inc.
Sustained-release morphine has a half-life of from 8 to 12 hours.
"You can give it at hour zero and maintain a blood level
for 12 hours," said Dr. Blum, deputy director, Kaplan Comprehensive
Cancer Center, New York University Medical Center. Morphine sulfate
solution has to be given every 4 hours.
Patients can be started directly on sustained-release morphine
or can be converted from other opioid narcotic analgesics, he
said. "What we tend to do, and what I recommend, is to start
out with immediate-release morphine and gradually, over time,
as the patient stabilizes, convert to MS Contin."
Since it takes time to reach steady- state concentrations with
the sustained-release form, patients should continue to take an
immediate-release morphine preparation for several days after
starting the sustained-release drug, he said.
Dr. Blum stressed that the enteral route should be used if possible,
ie, any access routes to the GI tract (oral, buccal, rectal, tube).
Approximately 30 mg of oral morphine is equivalent to 10 mg of
injected morphine, he said. Roughly 4 mg of oral hydromorphone
is equivalent to 15 mg of oral morphine.
Methadone probably should not be used for patients with chronic
severe pain, because of the long half-life of the toxic metabolites,
Dr. Blum warned. Similarly, meperidine (Demerol), although highly
effective when given parenterally at 75 mg for acute pain, is
not recommended for the management of chronic pain. The equal
oral analgesic dose is 300 mg, which, over time, is associated
with a high degree of side effects (primarily sedation).
Fentanyl Patch an Alternative
Dr. Blum singled out fentanyl as a well-tolerated alternative
to oral analgesics. Fentanyl is used in the operating room for
anesthesia and has been available for a number of years as a transdermal
patch (Duragesic). "The problem with fentanyl is that it's
very short acting," he said, "but the patch allows continuous
release through the skin."
Fentanyl is particularly useful for people who do not have an
enteral tract available, or have nausea and vomiting and cannot
take oral medication. At about 50 mcg per hour, it is approximately
equivalent to 30 mg of morphine by mouth or 10 mg given parenterally,
Dr. Blum said.
Because of its slow onset of action, patients should take a short-acting
narcotic analgesic while building up their fentanyl dose, he said.
"But it does arrive at a steady state and does last from
48 to 72 hours; the patch can be replaced approximately every
3 days ".